Combined wet and dry coolers usually comprise one or more openings constituting a first air inlet and a wet heat exchange unit in which the air from the first inlet is placed in direct contact with the liquid to be cooled and a dry heat exchanger unit whose exchange elements may be disposed vertically at the periphery of the tower adjacent one or more openings constituting a second air inlet in parallel with the first. In the dry heat exchange unit the air is not in direct contact with the liquid, the latter flowing in heat exchange elements, for example, finned tubes or smooth tubes of metal or synthetic material. These coolers may employ a natural draught or a forced draught produced by suction or blower fans.
Such combined coolers are designed to avoid at the air outlet of the installation the formation of clouds which usually occurs at the air outlet of conventional wet coolers. In the past avoidance of air outlet clouds has only been partly achieved and there often remain cloudy streams which result from an insufficient mixture of the hot and humid air, which issues from the wet exchanger and flows at the centre of the tower, with the hot dry air which issues from the dry heat exchanger.
To overcome this problem of the mixture of the two air streams, it is known to dispose inside the cooling tower deflecting surfaces which produce turbulence in the dry air current and direct it toward the centre of the tower.
In some arrangements, these deflecting surfaces are formed by curved guide vanes which engage the humid air current and impart a giratory motion to the dry air to improve mixing of the two air streams.
It is also known in the prior art to provide a cooling tower at the base of which the gas stream which enters the installation passes through at least one heat exchange device, and at least one deflector disposed in the tower above the heat exchange device and adapted to direct at least a part of the gas stream toward the periphery of the tower.